oded_vaalany, eranston Oded Vaalany (208230474), Eran Ston (206704512) EX: 2

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REMARKS:

AMSWERS:

1.a: Describe what the functions sigsetjmp and siglongjmp do?

sigsetjmp - saves the current location, CPU state and signal mask.\
siglongjmp - goes to the saved location' restoing the state and the signal mask

1.b: Describe how sigsetjmp and siglongjmp affect masking?

sigsetjmp saves the current mask and whan siglongjmp called he modify the
signal mask to the same signal as the saved state of the sigsetjmp he restores

2: Describe one general use of user-level threads and explain why user-level
threads are a reasonable choice for your example?

When you have a few threads of calculations only, without any requests from the
os. such as two diffrents calculations in the same program. \
so the user level is preferd because: Threads switching in user level is cheaper,
and scheduling can be application-specific so the developer has more control over
what calculation is more importent at each time. this allow the programer to fit
his programs batter to the hardware.

3: Google’s Chrome browser creates a new process for each tab. What are the
advantages and disadvantages of creating the new process (instead of creating a
kernel-level thread)?

disadvantages:

-   processes has more overhead than kernel-level thread
-   its more time the kill/create a proccesses than a kernel-level threads

advantages:

-   protected from each other require os to communicate
-   process has the abilty to scheduled by theirselves and its allow to the
    tabs stop their actions while not in use
-   errors are contained within the process (tabs) and not effect the other
    processes (tabs)

4.a: Open an application (for example, “Shotwell” on one of the CS computers).
Use the “ps -A” command to extract the application’s pid (process ID).

the keyboard generates an interrupt signal when we enter the kill command in the shell. The shell sends a signal to the operating system to kill the Shotwell process with the specified PID. The operating system sends a SIGTERM signal to the Shotwell process, and if necessary, a SIGKILL signal to forcefully terminate it. The Shotwell process receives these signals and handles them accordingly.
#TODO

5: What is the difference between ‘real’ and ‘virtual’ time? Give one example
of using each?

real time is the time that took to run the process in the physical world
including all the breaks, and virtual time is the time the proccess think he
ran. for example we have a proccess who run 3 times on the cpu in one minute
each time was 10 seconds. so in the virtual time the process ran 30 seconds
while in the real time (world) the process ran 60 seconds from start till the
end

real time example in the a factory we want to mesure the time took to run the
process, we will determine the time in real time, because its importent that
each proccess fit the real world sceduale

virtual time example, when the os want to manage its RAM sapce it swaps the
data of each procces between the RAM to the Hard Disk by pay attantion to the
virtual time of the procces and not the real time of the process